Iac Driver missing from external instrument

Hi there, I am trying to send midi out of ableton into MainStage 2 , using the Iac driver. I have set this is before using mac os 10.6.8 , but have installed mavericks 10.9.4 as some of my plugins require a newer os to function. I have set up Iac drivers before, and this still works for my studio system. Since I plan to play live with a band, Im using ableton for trigger clips, using effects etc... but I want to use the Iac driver to send midi out of ableton to another app MainStage. I can see the Iac driver ports (buses) that I created in midi preferences in ableton, the problem is when I add an external instrument I can't seem to select an Iac port in the midi drop down menu in the external instrument. Not sure if it is an ableton problem or os problem. I have clean installed twice now but still no luck. Im using a macbook pro 8.2